问更改当前分支并保持本地更改

EN

git checkout --detach # disconnect from A
git reset --soft b # set the branch pointer to whatever revision B is pointing to.... Your working tree will be unaffected
git add . # add everything to index
git commit -m "revision after B that made it look the way I had it where I was working"
# if you like everything, move b branch to this revision and push
git branch -f b
git checkout b
git push some-remote b

# get the uncommited changes on the branch
git commit -am "Useful message"

# point b where a is now
git branch -f b a

# instead of forcing the branch we could merge with a strategy ours
# but it's hard to tell what you need from your description alone

# reset a to its previous state
git reset --hard HEAD^

C1---C2 <<< a <<< HEAD # with a dirty tree, uncommited changes

      ? <<< b # (you didn't mention where b was pointing)

C1---C2 <<< a <<< HEAD
     \
      C3 <<< b # where your last (previously uncommited) changes are

# we work on a copy of branch a
git checkout -b a-copy a

# get the uncommited changes on the branch
git commit -am "Useful message"

# proceed with the merge, taking nothing from b
git merge -s ours b

# we now reflect the merge on b, and this is a fast-forward
git checkout b
git merge a-copy

# no further need for the working copy of a
git branch -D a-copy

C1---C2 <<< a
     \
      C3 <<< a-copy <<< HEAD

      o <<< b (anywhere in the tree)

C1---C2 <<< a
     \
      C3 (same state as a, plus the previously uncommited changes)
       \
        C4 <<< a-copy <<< HEAD (the merge taking only C3 side)
       /
      o <<< b (anywhere in the tree)

C1---C2 <<< a
     \
      C3 (same state as a, plus the previously uncommited changes)
       \
        C4 <<< b <<< HEAD
       /
      o